Title: Further studies of L-arginine biosynthesis in germinating pea seeds. Evidence for the presence of argininosuccinate synthetase in cotyledon extracts
Abstract: The synthesis and metabolism of arginine in germinating peas was examined by supplying micromolar quantities of L-citruiline-carbamyl- 14 C, DL-arginine-carbamyl- 14 C, and DL-arginine-5- 14 C to imbibing seeds. Citrulline was readily incorporated into arginine, but the labelled arginine solutions were not extensively metabolized.Extracts of 1-day-old cotyledons were found to catalyze the synthesis of arginine from citrulline in a reaction having absolute requirements for ATP, L-aspartate, and magnesium ions. The extracts were fractionated by (NH 4 ) 2 SO 4 precipitation followed by gel filtration on columns of Sephadex G-50 and G-200. These treatments increased the specific enzyme activity by approximately 36 times. After such treatments the preparations still contained appreciable amounts of argininosuccinate lyase (L-argininosuccinate arginine-lyase, EC 4.3.2.1) activity. The rate of arginine synthesis was altered by increasing the concentrations of L-citrulline, L-aspartate, and ATP. The latter compounds were found to be inhibitory at concentrations of 1 μmole/ml and 4 μmoles/ml, respectively. Arginine synthesis was markedly affected by pH and by additions of arginine and argininosuccinate. It is concluded that germinating pea cotyledons contain appreciable levels of argirrinosuccmate synthetase (L-citrulline:L-aspartate ligase (AMP), EC 6.3.4.5), and furthermore, that this enzyme has importance in arginine biosynthesis during germination.
Publication Year: 1969
Publication Date: 1969-04-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 11
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